In a typical wireless communication system, an area is divided geographically into a number of cell sites that are each defined by one or more radio frequency (RF) radiation patterns from a respective base transceiver station (BTS) antenna. Most cell sites are usually further divided geographically into a number of sectors that are each defined respectively by radiation patterns from directional antenna elements of the respective BTS antenna. The radiation pattern of each cell or cell sector produces an air interface that defines a respective coverage area.
Cell sites of the typical wireless communication system are operated by one or more wireless service providers (WSP). A WSP is a company that provides telecommunications through RF signals rather than (or in addition to) through end-to-end wire communication. A WSP may transmit signals using one or more carrier frequencies. A carrier frequency (or simply “carrier”) is a transmitted electromagnetic pulse at a steady frequency of alternation on which information can be imposed by increasing signal strength, varying the frequency, or other means.
Each cell site in a wireless communication system may support only a limited amount of wireless signal traffic, based at least in part on the number of carrier frequencies used by the cell site. Depending on where the cell site is located (e.g., in a rural area, or in an urban area), the WSP may choose to implement a greater or fewer number of carrier frequencies in the cell site, in order to support a commensurate, expected amount of traffic. As a result, various cell sites throughout the WSP's network may use different numbers of carrier frequencies.
In some wireless communication systems (such as those operating in accordance with the Code Division Multiple Access (CDMA) protocol, among others), numerous cell sites in a given market area will all use the same base carrier frequency, which can be referred to as F1. Depending on traffic requirements, certain ones of the cell sites may then additionally use a number of “overlay” carrier frequencies, such as F2, F3, and so forth. (The particular frequency (e.g., center frequency) of each of these carriers is not critical for this discussion.)
Furthermore, each carrier frequency used in a cell site may have an associated cost, in terms of power to drive communications on the carrier frequency, backhaul and other associated infrastructure to support communications on the carrier frequency, and perhaps a license to use the carrier frequency. Therefore, when a WSP adds an overlay carrier frequency to a cell site, the WSP may incur an incremental cost for doing so. It follows that a WSP may also be able to reduce costs by removing or “turning down” carrier frequencies that are not absolutely necessary to maintain an acceptable level of operation in the WSP's network.